1. Field of the Invention
An aspect of the present invention relates to methods of fabricating a thin film transistor and an organic light emitting diode display device having the same that can minimize defects of the device and increase production yield by preventing arcing during crystallization of a semiconductor layer due to Joule heat generated upon the application of an electrical field to a metal layer electrically connected to the semiconductor layer.
2. Description of the Related Art
Generally, annealing techniques include a furnace annealing technique using a heat furnace, a rapid thermal annealing (RTA) technique using radiant heat such as a halogen lamp, a laser annealing technique using laser, and an annealing technique using Joule heat. The annealing techniques are determined according to characteristics of the material and process, such as a range of an annealing temperature, uniformity of the annealing temperature, a heating rate, a cooling rate, purchase price, and maintenance cost. Particularly, when high temperature annealing is needed, or high rate annealing is needed only in a local region of a material due to characteristics of the material and process, the selection of annealing techniques is very limited.
The laser annealing technique can rapidly anneal a surface of the material, but laser annealing applies to only a limited set of materials because the possibility of the annealing is determined according to the kind of material to be annealed. Particularly, since scanned linear laser beams overlap when annealing a large-sized device, non-uniformity in intensity of the laser beam and non-uniformity in irradiation level of the laser beam by time can occur. Also, laser annealing requires very expensive equipment having a high maintenance cost.
The RTA technique is widely applied to semiconductor fabrication processes, but current RTA technology can not be applied to silicon wafers larger than 300 mm in diameter. As a result, it is difficult to apply the RTA technique on very large substrates. Moreover, RTA has a maximum heating rate of 400° C./sec, and thus cannot be applied to a process requiring a higher heating rate.
Thus, research has been widely conducted on annealing techniques which can solve these problems and are free from processing limitations. Among them, a rapid annealing technique performed by applying an electrical field to a conductive layer and generating Joule heat can rapidly anneal a selected material by transfer of high heat, and has a much higher heating rate than the RTA technique. However, the above technique using Joule heat generated by the application of the electrical field cannot prevent physical detects due caused by arcs generated by the Joule heat.